Lighthouse
a lofty tower or other structure, erected at the entrance of a harbor, or at some important or dangerous part of a coast, and having a strong light at the top, to guide vessels, and were lighted up with fires, but now oil, gas, and electricity are used, the power of the light being increased by the adopgas, and electricity are used, the power of the light being increased by the adopprisms. In the United States these matters are under the supervision of the Lighthouse Board. The most important lighthouse in the United States is the great tower PETIT-MANON GRANITE TOWER LIGHT- HOUSE, MAINE of a lighthouse-viz., sending the great- est number of rays of light toward the horizon. As an example of a modern lighthouse tower we may take Skerryvore, which is 139 feet height feet in diameter at the base, containing a mass of 58,580 cubic feet of granite. (See EDDYSTONE.) lighthouse tower we may take Skerry To Augustin Fresnel belongs the honor of inventing and first employing, in 1822, the dioptric system for lighthouse purposes in combination with a central lamp having four concentric wicks. He devised the lighthouse lens, which is planoconvex, 3 feet 3 inches in height by 2 feet 6 inches in breadth, composed of a central disk, surrounded by annular rings gradually decreasing in breadth as they recede from the center. If these lenses be assembled on a frame with eight or more sides, having a lamp in about ce the by thunder distant, NING AB sed in teleg ough the are attack lly serrated rests on the grow ENG COND ed to prote against de LIGHTNING duced. The electric light was first shown revolve, a dioptric revolving light is produced. The electric light was first shown DAM LIGHT SERVICE SERVICE ROOM BED ROOM LOW LIGHT ROOM LIVING ROOM CRANE ROOM STORE ROOM OIL ROOM OIL ROOM ENTRANCE WATER TANK DAM SECTION OF EDDYSTONE LIGHTHOUSE to the mariner in 1858 from the Foreland lighthouse.